Method of continuously casting metals and apparatus for the same

ABSTRACT

This invention is to carry out a continuous casting by melting a metal or compound which has a specific gravity higher than the specific gravity of a metal to be continuously cast, keeping the melting temperature at a temperature lower than the melting point of the metal to be continuously cast and cooling the molten metal to be continuously cast with the melt having had the melting temperature thus regulated while floating it on the surface of said melt.

O United States Patent 1111 3,5

[72] Inventor Tatsuo Kuratomi [56] References Cited 2- g g 'e Chigasaki, UNITED STATES PATENTS [21] A I No 2,316,144 4/1943 Coxe 164/81 [22] ff min 1968 2,754,559 7/1956 Fromson l64/82X [45] Patented Feb: 1971 3,430,680 3/1969 Leghorn 164/81 1 [32] Priority Oct. 10, 1967, June 7, 1968 Primary ExaminerCharles W. Lanham [33] Japan Assistant ExaminerV. K. Rising [3] 42/65713 and 43/38767 Att0rney0tto John Munz METALS ABSTRACT: This invention is to carry out a continuous cast- 2 Cl 1D ing by melting a metal or compound which has a specific suns rawmg gravity higher than the specific gravity of a metal to be con- [52] U.S. Cl 164/82, tinuously cast, keeping the melting temperature at a tempera- 164/81 ture lower than the melting point of the metal to be continu- [51] lnt.Cl 822d 11/00 ously cast and cooling the molten metal to be continuously [50] Field of Search 164/81, 82 cast with the melt having had the melting temperature thus (S) regulated while floating it on the surface of said melt.

E I/ f METHOD OF CONTINUOUSLY CASTING METALS AND APPARATUS FOR THE SAME This invention relates to a method of continuously casting metals and their continuously casting apparatus.

This invention is to carry out a continuous casting by melting a metal or compound which has a'specific gravity higher cooling the molten metal to be continuously cast with the melt having had the melting temperature thus regulated while floating it on the surface of said melt. i

In the present invention, for the raw material substance of the melt to act to cool the molten metal to be continuously cast while floating it is to be used a metal or compound which has a specific gravity higher than the specific gravity of the metal to tie-continuously cast, has a melting point lower than the melting point of said metal, has a boiling point higher than the melting point of said metal, produces no alloy with said meta! and causes no chemical reaction with it. For the raw material substance of such melt can be used such metal of a high specific gravity aslead, such compound of a high specific gravity as lead oxide or. such glass compound of a high specific gravity as lead glass. Such metal or compound which is proper for the metal to be continuously cast is selected from them to be a raw material substance of the melt.

In carrying out the continuous casting of the present invention, a metal or compound meeting the requirements is made a raw material substance of a melt, the melt prepared by melting the raw material substance is maintained at a temperature lower than the melting point of a metal to be continuously cast and the molten metal to be continuously cast is cooled to be coagulated with said melt having had the melting temperature thus regulated and maintained while said molten metal is being floated and moved on the surface of said melt. Therefore, it isnecessary to cool and adjust the melt which is to cool and coagulate the molten metal to be continuously cast while floating and moving it so that the temperature of said melt may be a temperature lower than the melting point of the metal to be continuously cast and that the temperature most adapted to the continuous casting may be always maintained. It is also necessary to melt the metal or compound which is a, raw material substance of said melt before starting the continuous casting and to heat it to a temperature adapted to carry out the continuous casting. Therefore, as a means of melting the raw material substance of the melt and then elevating the temperature of the melt to a temperature adapted to carry out the continuous casting, a melt tank is equipped with a heating device and, as a means of preventing the melting temperature of the melt kept molten in the melt tank from rising to be above a fixed temperature by being heated by the heat of the molten metal fed to be continuously cast and of maintaining the temperature of said melt always at the fixed temperature, the melt tank is equipped with a cooling device.

When the continuous casting of the present invention is to be carried out, the molten metal to be continuously cast is floated on the surfaceof the melt contained in the melt tank and is continuously being floated from one side to the other. Therefore, a molten metal feeding port is provided on one side of the melt tank and a coagulated metal delivering port for continuously taking out the coagulated metal coming as coagulated on the surface of the melt is provided on the other side of the tank. Said molten metal feeding port is equipped with a molten metal feeding device for feeding the molten metal by a fixed amount per unit time at a fixed velocity and said coagulated metal delivering port is equipped with a coagulated metal delivering device for continuously taking out the coagulated metal coming as coagulated continuously on the surface of the melt in the melt tank.

When the continuous casting of the present invention is to be carried out, as the upper surface of the molten metal to be continuously cast is in contact witha gas, the gas with which the surface of the molten metal is in contact is made a reductive or inert gas so that the molten metal to be continuously cast and the coagulated metal may not be oxidized.

An object of the present invention is to provide a method of continuously casting a metal of a thin layer in which the upper and lower surfaces of the coagulated metal are flat and smooth. 7

Another object of the present invention is to provide a method wherein is obtained a material excellent as a metallic material to be rolled without oxidizing the upper surfaces of the molten metal and its coagulated metal. a

A further object of the present invention is to provide a continuously casting apparatus wherein the upper surfaces of the molten metal and its coagulated metal are not oxidized.

The accompanying drawing is a view illustrating an embodiment of the apparatus for working the method of the present invention.

This embodiment relates to the case of continuously casting a soft steel of a carbon content of about 0.2 percent. The soft steel of a carbon content of 0.2 percent is of a melting point of about b 1.535 C. and a specific gravity of 7.86 as a solid or 6.9 as a molten metal. Therefore, it is an essential condition that the melt to be used to cool and coagulate the molten metal of the soft steel while floating it should be of a metal or compound which has a melting point lower than l,535 0, point higher than l,535 C. and a specific gravity higher than 7.86, produces no alloy with the soft steel and causes no chemical reaction with it. From the metals and compounds meeting such essential co nditions, metallic lead. is selected in the present embodiment. The metallic lead is of a melting point of 327 C., a boiling point of 1,750 C. and a specific gravity of 11.3 produces no alloy with the sofi steel in the-industrial precision and causes no chemical reaction with it. Therefore, in the ease of continuously casting the molten metal of the soft steel, the metallic lead is a substance proper as a raw material substance of the melt to act to cool and coagulate the molten metal of the soft steel while floating it.

in the drawing, 1 is a melt tank body lined with a refractory material 2 on the inside surface. 3 is a lead melt and the surface 4 of the melt is maintained always at a fixed level. 5 is a gastight chamber forming the upper part of the melt tank body 1 and filled with a nitrogen gas which is aninert-gas. 6 is a molten metal feeding port. The surface of the molten metal 10 is maintained always at a fixed level. 7 is a molten metal feeding device for maintaining at a fixed level the surface of the molten metal 10 in the molten metal feeding port 6 while adjusting with a stopper 9 the molten metal 8 coming by being conveyed by a ladle or any other means. 13 is a coagulated metal 12 delivering port for taking out the coagulated soft steel 12 made by cooling and coagulating with said lead melt 3 the molten metal 11 of the soft steel fed through the molten metal feeding port 6 and floated on the surface of the lead melt 3 while floating it on the surface of the lead melt. 14 is a coagulated metal delivering device consisting of pinch rolls 15 for pulling the coagulated soft steel 12 out of the coagulated metal delivering port 13. 16 is a solid lead heating and melting device fitted in the melt tank body 1 and consisting of a hollow cylinder having a burner 17 in it. 18 is a cooling device for cooling the lead melt 3 in a molten state in the melt tank body 1 so that the temperature of the melt may not be elevated to be above a fixed temperature by being heated by the heat retained by the molten metal of the soft steel fed onto the surface of the melt. It is a hollow cylinder having a water injector 19 in it. The upper part of the melt tank 1 forms a gastight chamber 5 and is filled with a nitrogen gas 20 which is an inert gas under a slightly positive pressure. When a soft steel is to be continuously cast by using a continuous casting apparatus forming such mechanism, a molten metal 8 of the soft steel refined with a converter or open-hearth furnace is first conveyed into the molten metal feeding device 7 by a ladle or any other means, is poured into the molten metal feeding port 6 at a flow volume and velocity regulated with the stopper 9 so that the feed per unit time may be as fixed, is then fed to float on the surface of the lead melt 3 in the melt tank 1 while its surface is maintained at a fixed level, is cooled while floating and moving on the surface of the lead melt 3, moves toward the coagulated metal delivering port 13 and becomes the coagulated soft steel 12 before said delivering port 13. The lead melt 3 in such case tends to elevate the temperature to be above the fixed temperature by being heated by the molten metal of the soft steel and is therefore cooled with the lead melt cooling device 8 so as to be maintained always at about 500 C. As described above, the lead is of a melting point of 327 C. and a boiling point of 1,750 C. As the melting point of the soft steel is 1,535 O, the molten metal of the soft steel can be cooled and coagulated in the temperature range between the melting point and boiling point of the lead. Further, as the lead is of a specific gravity of 1 1.3 and the soft steel is of a specific gravity of 7.86 as a solid or 6.9 as a molten metal, the soft steel either as a molten metal or as a coagulated metal can be floated on the melt of the lead. Further, as the soft steel and lead produce no alloy in the industrial producing operation and cause no chemical reaction with each other, even though the lead melt and the molten metal of the soft steel come into contact with each other, no trouble will be caused. Thus, the soft steel coagulated on the surface of the lead melt 3 is taken out by being held by the pinch rolls 15 of the coagulated metal delivering 14 through the coagulated metal delivering port 13. The water injector 19 is provided in the cooling device 18 for preventing the temperature rise of the lead melt 3 so that the temperature of the lead melt 3 may be regulated by adjusting the volume of injected water. In starting the continuous casting, as it is necessary to heat and melt the solid lead contained in the melt tank body 1, the solid lead is heated to be the lead melt 3 with the heating device 16 provided in the melt tank body 1. The burner 17 is provided in the heating device 16 so that the operation of melting the solid lead may be regulated by adjusting the burner. The gastight chamber forming the upper part of the melt tank body 1 is filled with the nitrogen gas 20 which is an inert gas so that the molten metal of the soft steel cooled and coagulated while floating on the surface of the lead melt 3 in the melt tank body 1 and the thus coagulated meta of the soft steel may not be oxidized. The pressure of this nitrogen gas 20 is made slightly higher than the atmospheric pressure so that no outside air may flow into the gastight chamber 5. When the continuous casting is thus carried out, the molten metal 11 of the soft steel will coagulate in contact with the surface of the lead melt 3 forming a flat smooth liquid surface and therefore the lower surface of the coagulated metal 12 of the soft steel after the molten metal 11 coagulates will be a flat smooth surface. Further, the upper surface of the molten metal 11 of the soft steel will coagulate in the state of a flat smooth molten metal surface in contact with the nitrogen gas 20 which is an inert gas and therefore the upper surface of the coagulated metal 12 of the soft steel will be also a flat smooth surface.

As evident from the above explanation, when a metal is continuously cast by the continuous casting method of the present invention by using the continuous casting apparatus of the present invention, as the lower surface of the continuously cast molten metal is the flat smooth liquid surface of them the melt of a metal or compound with which the lower surface of the molten metal is in direct contact, the lower surface of the molten metal coagulating on said flat smooth liquid surface will be a flat smooth surface. Further, as the upper surface of the molten metal on the flat smooth surface of the melt coagulates in contact with the reductive or inert gas, said upper surface of the molten metal will coagulate also as a flat smooth surface. Further, as the gas in contact with he upper surface of the coagulating molten metal is a reductive or inert gas as mentioned above, the upper surface of the molten metal will coagulate as a metallic surface not oxidized. Therefore, the metal continuously cast by the continuous casting method of the present invention by using the continuous casting apparatus of the present invention is a material very excellent as a metallic material to be rolled.

The above mentioned embodiment 15 described of the case that the metal to be cast is iron and lead is used for the compound which has a melting point lower than the melting point of iron, has a boiling point higher than the melting point of iron, produces no alloy with iron and causes no chemical reaction with it. Further, the case that the metal to be cast by them the method according to the present invention is aluminum shall be explained.

If a melt of a compound which is lower in the melting point than aluminum and is higher in the specific gravity than aluminum is contained in the tank as a cooling medium, the temperature of the melt is kept a a temperature lower than the melting point of aluminum and a molten metal of aluminum is fed at one end of the tank containing the cooling medium, as the above mentioned melt is of a specific gravity higher than of them the molten metal of aluminum, the molten metal of aluminum will flow toward the other end of the tank while floating on the above mentioned melt. The above mentioned melt is cooled with the cooling device and acts as a cooling medium. The molten metal of aluminum floating and flowing on such cooling medium is cooled to coagulate. The thus coagulated aluminum is continuously pulled out of the outlet at the other end of the tank to obtain continuously cast aluminum.

The compound melt to float the molten metal of aluminum must be such as is not only of a melting point lower than of aluminum and a specific gravity higher than of coagulated aluminum and molten aluminum but also produces no alloy and compound with aluminum. The method of the present invention is characterized by using as such substance one or more of such compounds as calcium iodide, magnesium iodide and lithium iodide. The melting points and specific gravities of these compounds and aluminum are shown-in the following table:

Melting point, Specific Substances C gravity Remarks Al 660.2 2. 699 It coagulates the molten metal. Cal: 575 3. 956 Each of them is made a melt to cool Mgh 650 4. 256 and coagulate the molten metal of L11 446 4. 061 aluminum as a cooling medium.

As each of Ca, Mg and Li forming these compounds is stronger in the chemical activity than A1, each of Cal Mgl and Lil does not cause such chemical reaction as of being reduced by Al.

1 claim:

1. A method of continuously casting aluminum comprising the steps of:

providing a melt selected from a group consisting of calcium iodide, magnesium iodide and lithium iodide;

maintaining the temperature of said melt below the melting point of aluminum;

feeding molten aluminum onto the surface of said melt;

cooling the aluminum while being floated until coagulated;

and

removing the coagulated aluminum from the surface of said e melt continuously.

2. A method as in claim 5, said step of feeding molten aluminum upon the surface of said melt being maintained continuously in the same direction from one end of the surface of said melt across it, whereby due to the lower specific gravity of the molten aluminum the aluminum flows floatingly on the said melt toward the opposite end of said surface from where it is removed. 

2. A method as in claim 5, said step of feeding molten aluminum upon the surface of said melt being maintained continuously in the same direction from one end of the surface of said melt across it, whereby due to the lower specific gravity of the molten aluminum the aluminum flows floatingly on the said melt toward the opposite end of said surface from where it is removed. 